Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$57.47	12.406%	$64.5997	$64.60	$64.60	$64.60
Purchase #2	$14.30	7.263%	$15.3386	$15.34	$15.35	$15.30
Purchase #3	$128.89	10.107%	$141.9169	$141.92	$141.90	$141.90
Purchase #4	$91.65	5.241%	$96.4534	$96.45	$96.45	$96.50
Purchase #5	$144.48	5.468%	$152.3802	$152.38	$152.40	$152.40
Purchase #6	$125.90	12.790%	$142.0026	$142.00	$142.00	$142.00
Purchase #7	$82.95	13.707%	$94.32	$94.32	$94.30	$94.30
7 purchase totals =	$645.64		$707.0114	$707.01	$707.00	$707.00